1. Field
A combined power switching system for charging and operating battery-powered electric traction motors is disclosed.
2. General Background
Most power-using transportation vehicles—specifically, power-propelled surface vehicles, such as automobiles, motorcycles, wheeled and tracked recreational vehicles, buses, trucks, and trains; water-borne vehicles, such as commercial and recreational boats and ships, buoys, manned and unmanned submersibles, etc.; and aerial vehicles, such as airplanes, airships, and balloons—combine a need for storage of potential energy and a need to convert that energy into a readily-used form. Such advantage as may be gained from small size and low mass constrains storage and conversion apparatus. For a few centuries, wood, followed by coal, then diesel fuel, has been burned in air to release heat to generate steam that directly drive locomotives over rails. A portion of power for rail transportation—now virtually all of that power—has been supplied in the form of electricity from remote or on-board power generators, or in the form of torque from diesel-fuel powered shaft-output engines. For about a century, much of the world-wide transportation network has used the burning of gasoline, diesel fuel, and/or alcohol to generate shaft torque to directly drive vehicles over roads, as well as powering ships, aircraft, etc.
For the last few decades (i.e., for 20-30 years, plus limited experimentation since ca. 1900), combustible gases (methane, hydrogen, etc.) and stored electricity have been applied to powered vehicles in place of complex hydrocarbons, in pursuit of benefits such as reversal of trends of habitat destruction, and to advance development of ecologically-sound (sometimes termed “green”) technologies. Specific “green” vehicle applications include rechargeable electric power sources for surface vehicles and hybrid versions thereof. The latter typically use both in-vehicle combustion technology and stored electricity, ultimately to provide shaft torque for wheel or propeller-driven propulsion.
The components used for battery-powered and hybrid vehicles suffer performance penalties when the relatively high volumetric and mass efficiency of liquid fueled combustion engines is compared to the low energy density of batteries and the further penalty hybrids have from carrying both technologies and using them either in alternation or simultaneously. Acceleration and wind drag penalties attributable to extra mass and volume are known to offset “earth friendly” benefits to a variable degree. To a greater extent than designers of vehicles using liquid-fueled combustion engines, which generally receive oxygen for combustion from the air and discharge their combustion products back into the air with impunity, designers of electric-powered vehicles commonly pay considerable attention to minimizing waste heat, which begins as stored chemical energy in battery systems, and which is dissipated in lieu of extending vehicle travel range.
Increasing storage system (i.e., battery) energy density and reducing mass of components other than the storage system, managing thermal spikes, cooling components that enable necessary actions such as battery charging, and providing power for motive force are desiderata.